US5438399A - Image forming apparatus having transfer voltage control - Google Patents

Image forming apparatus having transfer voltage control Download PDF

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Publication number
US5438399A
US5438399A US08/182,384 US18238494A US5438399A US 5438399 A US5438399 A US 5438399A US 18238494 A US18238494 A US 18238494A US 5438399 A US5438399 A US 5438399A
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United States
Prior art keywords
voltage
image
bearing member
image bearing
constant current
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Expired - Lifetime
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US08/182,384
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English (en)
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Jun Asai
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Canon Inc
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Canon Inc
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Priority to US08/182,384 priority Critical patent/US5438399A/en
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/14—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base
    • G03G15/16—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer
    • G03G15/1665—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer by introducing the second base in the nip formed by the recording member and at least one transfer member, e.g. in combination with bias or heat
    • G03G15/167—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer by introducing the second base in the nip formed by the recording member and at least one transfer member, e.g. in combination with bias or heat at least one of the recording member or the transfer member being rotatable during the transfer
    • G03G15/1675—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer by introducing the second base in the nip formed by the recording member and at least one transfer member, e.g. in combination with bias or heat at least one of the recording member or the transfer member being rotatable during the transfer with means for controlling the bias applied in the transfer nip

Definitions

  • the present invention relates to an image forming apparatus such as an electrophotographic machine or an electrographic printer, more particularly to an image forming apparatus having an image transfer means in the form of a transfer roller.
  • an image transfer means having a contact type transfer roller or a transfer belt is contacted to an image bearing member to form an image transfer position in the form of a nip formed therebetween.
  • the transfer means supplied with an image transfer bias, by which the toner image is transferred from the image bearing member onto the transfer material.
  • an image forming apparatus such as a copying machine is usable with different kinds of transfer materials.
  • the area in which the image bearing member or the transfer roller is in contact with the transfer material is different.
  • the transfer bias is applied, the area in which the transfer means is directly contacted to the image bearing member is different because the size of the transfer material is different. Therefore, it is difficult to flow substantially constant current only through the transfer material irrespective of the transfer materials.
  • the problem also arises from the thickness or the material of the transfer material as well as the size of the transfer material.
  • the constant current control through the transfer material is not satisfactory because the amount of charge applied to the transfer material sometimes is sufficient with the result of improper image transfer and a smaller toner retaining power on the transfer material leading to the scattering of the toner or the disturbance of the image.
  • the size of the transfer material supplied is so large that the contact area between the transfer roller and the image bearing member is too small, the constant current control through the transfer material is also unsatisfactory because the amount of electric charge applied onto the transfer material is sometimes too large, with the result that the toner is electrically charged to the polarity opposite to the right polarity, which leads to local image transfer void.
  • the transfer bias is constant-voltage-controlled.
  • the roller or the belt used for the transfer roller or the transfer belt has a resistance significantly changing depending on the ambient condition, particularly the humidity, although the change is also different depending on the materials used.
  • paper which is most frequently used as the transfer material has the resistance significantly dependent on the ambient condition. Therefore, it is difficult to effect the stabilized image transfer operation irrespective of the size or the material of the transfer material or the ambient condition.
  • the voltage level obtained by the constant current control is small. If, at this time, the resistance of the transfer material is large, the bias voltage required during the constant voltage control is large, because it is a sum of a voltage across the drum, the voltage across the transfer roller and the voltage across the transfer material. Because, however, the bias voltage provided in the constant current control is small, a required bias voltage is not provided. This results in less electric charge on the transfer material, and therefore, improper image transfer or disturbance of the image.
  • FIG. 1 is a side view of a major part of an image forming apparatus according to an embodiment of the present invention.
  • FIG. 2 is a timing chart illustrating operation of the apparatus of FIG. 2.
  • FIG. 3A is a sectional view in which a transfer material is present between the photosensitive member and the transfer roller.
  • FIG. 3B shows an equivalent circuit of the state of FIG. 3A.
  • FIG. 4 is a graph of voltage-current characteristics of the transfer roller under a low temperature and low humidity condition.
  • FIG. 5 is a graph showing voltage-current characteristics of an OHP sheet under the same ambient condition.
  • FIG. 6 is a graph of voltage-current characteristics of an OPC photosensitive member under the same ambient condition.
  • FIG. 7 is a graph of voltage-current characteristics under the same ambient condition when the sheet is not present and when the OHP sheet is present.
  • FIG. 8 is a graph of current-voltage characteristics of a transfer roller under a high temperature and high humidity condition.
  • FIG. 9 is a graph of voltage-current characteristics of an OPC photosensitive member under the same ambient condition.
  • FIG. 10 is a graph of voltage-current characteristics under the same ambient condition when the sheet is not present and when an OHP sheet is present.
  • an image forming apparatus having a cylindrical image bearing member (photosensitive member) 1 rotatable in a direction indicated by an arrow about an axis perpendicular to the sheet of the drawing.
  • the photosensitive member 1 is electrically charged to a negative polarity by charging means in the form of a charging roller 2 contacted to the photosensitive member 1 (a discharging wire is usable in place of the charging roller 2).
  • the charged photosensitive member 1 is exposed to light L in accordance with image information by an exposure means 3, by which an electrostatic latent image is formed on the photosensitive member 1 in accordance with the image information.
  • a developing means 4 develops the electrostatic latent image thus formed, with toner having been charged to a positive polarity into a visualized image.
  • the transfer roller having an axis extending in the same direction as that of the photosensitive member 1 is made of EPDM and is contacted to the photosensitive member 1.
  • the transfer roller 5 the toner image described above is transferred from the photosensitive member 1 onto the transfer material P in the transfer position which is the region between the photosensitive member 1 and the transfer roller 5.
  • the transfer material P has been fed along a conveyance passage 6.
  • the transfer bias of the negative polarity is applied to the transfer roller 5.
  • a clearance may be provided if it is smaller than the thickness of the transfer material P. In such a case, the transfer material P is pressed between the photosensitive member 1 and the transfer roller 5.
  • the transfer material P is separated from the photosensitive member 1, and is conveyed along the passage 6 to an unshown image fixing station wherein the toner image is fixed on the transfer material P.
  • the photosensitive member from which the image has been transferred is cleaned by a cleaning device 7, so that the toner remaining on the photosensitive member is removed to be prepared for the repeated image forming operation.
  • the transfer roller 5 is supplied with a predetermined bias voltage at predetermined timing in accordance with an image signal from a CPU (central processing unit) 9 by a voltage source (bias applying means) 8 which is capable of effecting constant voltage control and constant current control (ATVC: active transfer voltage control).
  • a voltage source (bias applying means) 8 which is capable of effecting constant voltage control and constant current control (ATVC: active transfer voltage control).
  • FIG. 2 shows the operational timing of the constant current control and the constant voltage control.
  • the constant current control is carried out when the sheet is absent from the transfer region, and a constant voltage control is effected when the sheet is present in the transfer region.
  • the voltage source 8 effects the constant voltage control to the transfer roller 5, and the voltage source 8 effects the constant current control during the other period.
  • the transfer roller 5 is constant-current-controlled when the non-image area of the photosensitive member 1 not having the toner image is in the transfer position, that is, when the transfer material is absent from the transfer position (non-passage period), as shown in FIG. 2.
  • a period occurs after the CPU 9 receives the image-on signal, more particularly, upon the pre-rotation period for the purpose of warming the fixing device up or in the sheet interval period between end of one sheet and a start of the next sheet when plural images are continuously formed.
  • the constant current through the transfer roller was -1 micro-ampere during the non-passage period. During this period, a basic datum for obtaining a voltage level required during the constant voltage control is obtained (V D ).
  • the voltage V D across the transfer roller 5 is stored in an unshown storing means.
  • the CPU 9 supplies a constant voltage control signal to the voltage source 8.
  • the voltage source 8 effects the constant voltage control to the transfer roller 5 with a constant voltage level which is provided by adding a predetermined constant voltage to the stored voltage V D .
  • the constant voltage control the toner image is transferred from the photosensitive member 1 to the transfer material P.
  • the voltage V D may be an average of plural samples of voltages during the constant current control period.
  • the voltage V actually applied to the transfer roller 5 during the constant voltage control (transfer operation) is determined in the following manner.
  • FIG. 3A schematically shows the state wherein the transfer material P is present in the transfer position.
  • FIG. 3B shows an equivalent circuit thereof.
  • the transfer roller is represented as a resistor, and the transfer material P and the photosensitive member 1 are represented by parallel circuits constituted by a resistor and a capacitor.
  • the voltage V applied to the transfer roller 5 during the period for transferring the toner image from the photosensitive member 1 to the transfer material P for effecting the proper image transfer operation is:
  • the efficiency of the toner transfer is maximum, and the image quality of the copy image is optimum.
  • the current level should not be larger and should not be smaller.
  • the electric charge (current) of the toner image per unit area is constant.
  • the optimum current flows per unit area of the toner image. Then, it is desirable that a transfer current providing it is obtained.
  • FIGS. 4, 5 and 6 show the voltage-current characteristics (V-I characteristics) of the transfer roller, the transfer material (OHP sheet) and the OPC photosensitive member under the low temperature and low humidity (15° C. and 10% RH).
  • FIG. 7 shows the V-I characteristics of all of them combined.
  • the line 0 V in FIG. 6 shows the V-I characteristics of the photosensitive member in the non-passage period, that is, when the photosensitive member is not electrically charged.
  • the line represented by "non-toner” represents the V-I characteristics of the charged photosensitive member without toner image (exposed area), and the line indicated by “toner” represents the V-I characteristics of the charged photosensitive member in the image portion (the portion deposited with the toner) (sheet passage period).
  • the curvature (1) represents the V-I characteristics during the non-passage period when the photosensitive member has the potential of 0 V relative to the transfer roller (that is, during the constant current control), and the curve (2) shows the V-I characteristics when the OHP sheet is passed through the transfer station.
  • the curve (1) in FIG. 7 is the V-I characteristics during the constant current control, and therefore, it is a sum of the V-I characteristics of the transfer roller (Vroll) shown in FIG. 4 and the V-I characteristics of the photosensitive member shown by 0 V curve of FIG. 6 Vdrum.
  • the curve (2) of FIG. 7 represents the V-I characteristics during the constant voltage control, and therefore, it is a sum of the curve (1), the V-I characteristics of the transfer material (Vpaper) shown in FIG. 5 and the added V-I characteristics "toner" over "OV” of FIG. 6 (Vdrum).
  • the optimum voltage V is selected so that the current of -1 micro-ampere flows through the transfer material P or through the toner image on the photosensitive member.
  • the transfer roller 5 is constant-current controlled during the sheet-non-passage period in which the transfer material is absent from the transfer position.
  • the voltage V D in FIG. 7 is a voltage when the constant current of -1 micro-ampere flows during the non-passage period. That is, it is the voltage (Vroll+V'drum) provided when a constant current flows through the circuit shown in FIG. 3B without paper with the charge potential of the photosensitive member being, when the constant current control is effected during non-passage period. Therefore, the voltage V D is the voltage during the constant current control providing the optimum current during the transfer operation.
  • V D -1.7 (KV) was provided.
  • V D -1.7 (KV) was provided.
  • the voltage V D is held for the purpose of the subsequent constant voltage control during the transfer action.
  • the optimum voltage level V during the constant voltage control is provided.
  • a toner image is on the photosensitive member or drum 1.
  • the transfer material P is present between the photosensitive member 1 and the transfer roller 5, the voltage corresponding thereto is added to the voltage V D .
  • the potential in the toner deposited portion is predetermined in the apparatus.
  • a voltage corresponding to the resistance of a highest resistance used in this apparatus (OHP sheet, for example) under the low temperature and low humidity condition (5° C., 10% RH, for example).
  • the voltage corresponding to the highest resistance of the transfer material is used. Therefore, no higher resistance of the transfer material is present in the apparatus, and the resistance of the transfer material is not higher than that in any used condition of the apparatus. Therefore, the voltage added to the detected voltage V D is constant.
  • the current through the transfer material at this time will be understood to be -1 micro-ampere from FIG. 7, and therefore, good image transfer operation is provided.
  • FIGS. 8 and 9 show the V-I characteristics of the transfer roller and the OPC photosensitive member under the high temperature and high humidity ambient conditions (32.5° C. and 90%RH).
  • FIG. 10 is the V-I characteristics when the transfer roller is combined with FIG. 5.
  • the V-I characteristics of the transfer roller are as shown in FIG. 8, which is different from that under the low humidity condition (FIG. 4).
  • the voltage across the photosensitive member is as shown in FIG. 9, and therefore, is not hardly different from that during under the low humidity (FIG. 6).
  • V D ' V'roll+V'drum
  • V1 Vpaper+Vdrum
  • the change in the resistance of the transfer roller can be, in effect, detected, and the good image transfer operation is possible irrespective of the resistance of the transfer material and the kinds of the transfer material.
  • the surface potential of the photosensitive member relative to the transfer roller during the constant current control is 0 V, but it is not limited to 0 V.
  • the constant current control is carried out when the surface potential of the photosensitive member is that after a blank exposure or that after the development.
  • the constant voltage added during the constant voltage control is only Vpaper.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
US08/182,384 1989-11-16 1994-01-18 Image forming apparatus having transfer voltage control Expired - Lifetime US5438399A (en)

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Application Number Priority Date Filing Date Title
US08/182,384 US5438399A (en) 1989-11-16 1994-01-18 Image forming apparatus having transfer voltage control

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Application Number Priority Date Filing Date Title
JP29628989 1989-11-16
JP1-296289 1989-11-16
US61300690A 1990-11-15 1990-11-15
US08/182,384 US5438399A (en) 1989-11-16 1994-01-18 Image forming apparatus having transfer voltage control

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5504565A (en) * 1994-03-11 1996-04-02 Canon Kabushiki Kaisha Image forming apparatus having transfer voltage timing control
US5570162A (en) * 1994-01-23 1996-10-29 Ricoh Company, Ltd. Charge depositing member and image forming apparatus using the same
US5598256A (en) * 1994-01-11 1997-01-28 Canon Kabushiki Kaisha Image forming apparatus
US5697015A (en) * 1996-05-29 1997-12-09 Lexmark International, Inc. Electrophotographic apparatus and method for inhibiting charge over-transfer
US5822651A (en) * 1996-03-28 1998-10-13 Samsung Electronics Co., Ltd. Transfer voltage adjusting device
US5873015A (en) * 1997-02-18 1999-02-16 Moore U.S.A. Inc. Like polarity biasing to control toner dusting
US6026257A (en) * 1997-09-22 2000-02-15 Canon Kabushiki Kaisha Image forming apparatus with constant current voltage control
US6516161B2 (en) 2000-03-16 2003-02-04 Canon Kabushiki Kaisha Image forming apparatus with surface potential detector
US20060013602A1 (en) * 2004-07-19 2006-01-19 Lee Beom-Ro Method and apparatus for controlling a fixer of a printer
US20070025749A1 (en) * 2005-05-19 2007-02-01 Masato Kubota Transfer control unit of an image forming apparatus
US20180148892A1 (en) * 2015-04-27 2018-05-31 Midas Safety Innovations Limited Polyurethane coated fabric

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0520819B1 (fr) * 1991-06-28 1998-08-19 Canon Kabushiki Kaisha Appareil de formation d'images comprenant un élément de chargement
DE69221787T2 (de) * 1991-07-01 1998-03-26 Minolta Camera Kk Kontaktaufladevorrichtung
JP3143521B2 (ja) * 1992-06-17 2001-03-07 シャープ株式会社 電子画像形成装置

Citations (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3781105A (en) * 1972-11-24 1973-12-25 Xerox Corp Constant current biasing transfer system
US4401383A (en) * 1980-10-16 1983-08-30 Olympus Optical Company Limited Transfer device for use in retention type electrophotographic copying machine
JPS5912469A (ja) * 1982-07-14 1984-01-23 Fuji Xerox Co Ltd 電子複写機の転写装置
JPS6114671A (ja) * 1984-06-29 1986-01-22 Matsushita Electric Ind Co Ltd 電子写真複写装置
EP0323226A2 (fr) * 1987-12-28 1989-07-05 Canon Kabushiki Kaisha Appareil de formation d'images
EP0338546A2 (fr) * 1988-04-20 1989-10-25 Canon Kabushiki Kaisha Dispositif à charger et appareil de formation d'images utilisant un tel dispositif
EP0367245A2 (fr) * 1988-11-02 1990-05-09 Canon Kabushiki Kaisha Appareil de formation d'images
JPH02123385A (ja) * 1988-11-02 1990-05-10 Canon Inc 画像形成装置
US4977430A (en) * 1988-06-24 1990-12-11 Eastman Kodak Company Transfer roller power supply
US5006902A (en) * 1987-06-30 1991-04-09 Canon Kabushiki Kaisha Image forming apparatus having a predetermined voltage applied to the transfer member
US5010370A (en) * 1988-10-29 1991-04-23 Canon Kabushiki Kaisha Transfer apparatus and image bearing apparatus using same having transfer means for contacting a backside of a transfer material
US5034777A (en) * 1989-06-20 1991-07-23 Canon Kabushiki Kaisha Transferring device having charging device with double oxide and voltage control
US5144368A (en) * 1989-11-15 1992-09-01 Canon Kabushiki Kaisha Charging device and image forming apparatus having same
US5179397A (en) * 1989-04-03 1993-01-12 Canon Kabushiki Kaisha Image forming apparatus with constant voltage and constant current control
US5253022A (en) * 1989-05-18 1993-10-12 Canon Kabushiki Kaisha Image forming apparatus

Patent Citations (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3781105A (en) * 1972-11-24 1973-12-25 Xerox Corp Constant current biasing transfer system
US4401383A (en) * 1980-10-16 1983-08-30 Olympus Optical Company Limited Transfer device for use in retention type electrophotographic copying machine
JPS5912469A (ja) * 1982-07-14 1984-01-23 Fuji Xerox Co Ltd 電子複写機の転写装置
JPS6114671A (ja) * 1984-06-29 1986-01-22 Matsushita Electric Ind Co Ltd 電子写真複写装置
US5006902A (en) * 1987-06-30 1991-04-09 Canon Kabushiki Kaisha Image forming apparatus having a predetermined voltage applied to the transfer member
EP0323226A2 (fr) * 1987-12-28 1989-07-05 Canon Kabushiki Kaisha Appareil de formation d'images
EP0338546A2 (fr) * 1988-04-20 1989-10-25 Canon Kabushiki Kaisha Dispositif à charger et appareil de formation d'images utilisant un tel dispositif
US4977430A (en) * 1988-06-24 1990-12-11 Eastman Kodak Company Transfer roller power supply
US5010370A (en) * 1988-10-29 1991-04-23 Canon Kabushiki Kaisha Transfer apparatus and image bearing apparatus using same having transfer means for contacting a backside of a transfer material
EP0367245A2 (fr) * 1988-11-02 1990-05-09 Canon Kabushiki Kaisha Appareil de formation d'images
JPH02123385A (ja) * 1988-11-02 1990-05-10 Canon Inc 画像形成装置
US5179397A (en) * 1989-04-03 1993-01-12 Canon Kabushiki Kaisha Image forming apparatus with constant voltage and constant current control
US5253022A (en) * 1989-05-18 1993-10-12 Canon Kabushiki Kaisha Image forming apparatus
US5034777A (en) * 1989-06-20 1991-07-23 Canon Kabushiki Kaisha Transferring device having charging device with double oxide and voltage control
US5144368A (en) * 1989-11-15 1992-09-01 Canon Kabushiki Kaisha Charging device and image forming apparatus having same

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5598256A (en) * 1994-01-11 1997-01-28 Canon Kabushiki Kaisha Image forming apparatus
US5570162A (en) * 1994-01-23 1996-10-29 Ricoh Company, Ltd. Charge depositing member and image forming apparatus using the same
US5504565A (en) * 1994-03-11 1996-04-02 Canon Kabushiki Kaisha Image forming apparatus having transfer voltage timing control
US5822651A (en) * 1996-03-28 1998-10-13 Samsung Electronics Co., Ltd. Transfer voltage adjusting device
US5697015A (en) * 1996-05-29 1997-12-09 Lexmark International, Inc. Electrophotographic apparatus and method for inhibiting charge over-transfer
US5873015A (en) * 1997-02-18 1999-02-16 Moore U.S.A. Inc. Like polarity biasing to control toner dusting
US6026257A (en) * 1997-09-22 2000-02-15 Canon Kabushiki Kaisha Image forming apparatus with constant current voltage control
US6516161B2 (en) 2000-03-16 2003-02-04 Canon Kabushiki Kaisha Image forming apparatus with surface potential detector
US20060013602A1 (en) * 2004-07-19 2006-01-19 Lee Beom-Ro Method and apparatus for controlling a fixer of a printer
US7269366B2 (en) * 2004-07-19 2007-09-11 Samsung Electronics Co., Ltd. Method and apparatus for controlling a fixer of a printer
US20070025749A1 (en) * 2005-05-19 2007-02-01 Masato Kubota Transfer control unit of an image forming apparatus
US20180148892A1 (en) * 2015-04-27 2018-05-31 Midas Safety Innovations Limited Polyurethane coated fabric

Also Published As

Publication number Publication date
DE69026199D1 (de) 1996-05-02
EP0428172A2 (fr) 1991-05-22
EP0428172A3 (en) 1992-03-11
DE69026199T2 (de) 1996-09-05
EP0428172B1 (fr) 1996-03-27

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